Pre-monsoon submicron aerosol composition and source contribution in the Kathmandu Valley, Nepal

Werden, Benjamin; Giordano, Michael R.; Goetz, J. Douglas; Islam, Md. Robiul; Bhave, Prakash V.; Puppala, Siva Praveen; Rupakheti, Maheswar; Saikawa, Eri; Panday, Arnico K.; Yokelson, R. J.; Stone, Elizabeth A.; DeCarlo, P. F.

doi:10.1039/d2ea00008c

Cited by 6 publications

(30 citation statements)

References 139 publications

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“…PM 2.5 and PM 10 concentrations at the two in-valley sites (Ratnapark and Lalitpur) were not significantly ( p = 0.33–0.34) different from each other but were significantly ( p < 0.001) higher than the more remote Dhulikhel site by a factor of 2.2–2.6 (Table ). Meanwhile, meteorological measurements, discussed and reported elsewhere, show similar conditions across the three sites, with slightly lower average temperature and relative humidity at Dhulikhel (7.8 °C, 67%, respectively) compared to Ratnapark (10.1 °C, 78%) and Lalitpur (11.2 °C, RH not available) . The average PM 2.5 concentrations at the in-valley sites (121–130 μg m –3 ) were similar to the average PM 2.5 concentrations observed in winter to spring of 2014 at six major roadways in the Kathmandu Valley (125 μg m –3 ) …”

Section: Resultssupporting

confidence: 77%

“…PM concentrations only had significant day/night variation at the Ratnapark site, where nighttime PM 10 concentrations were significantly ( p = 0.018) higher than the daytime concentrations. Meteorological measurements indicated semistagnant winds overnight (typically 0.5 m s –1 ) with a shallow boundary layer of ∼100 m depth compared to higher wind speeds during the day (1.5–2 m s –1 ) with a boundary layer of ∼800 m . Higher nighttime concentrations of PM in the Kathmandu Valley were observed previously at the Bode site and were explained by a shallower boundary layer, lower wind speed, cooler stagnant air, and favorable partitioning of gases to particles at higher relative humidity at night, especially for compounds with pH-dependent partitioning …”

Section: Resultsmentioning

confidence: 55%

“…Samplers were positioned to collect representative air samples and were placed atop buildings or other structures when possible. Colocated gas-phase, aerosol, and meteorology measurements are described elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…When combined with combustion source profiles developed in the first NAMaSTE, − we gain new insight to (i) the impact of garbage burning on ambient PM; (ii) the precursors to SOA, particularly aromatic VOCs; and (iii) the contributions of trace metals and dust to PM 2.5 and PM 10 . Our companion paper discusses the composition and sources of nonrefractory PM 1 measured by aerosol mass spectrometry with high time resolution and colocated measurements of meteorology and gases …”

Section: Introductionmentioning

confidence: 99%

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Wintertime Air Quality across the Kathmandu Valley, Nepal: Concentration, Composition, and Sources of Fine and Coarse Particulate Matter

Islam

Mahata³

et al. 2022

ACS Earth Space Chem.

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The Kathmandu Valley in Nepal experiences poor air quality, especially in the dry winter season. In this study, we investigated the concentration, chemical composition, and sources of fine and coarse particulate matter (PM2.5, PM10, and PM10–2.5) at three sites within or near the Kathmandu Valley during the winter of 2018 as part of the second Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE 2). Daily PM2.5 concentrations were very high throughout the study period, ranging 72–149 μg m–3 at the urban Ratnapark site in Kathmandu, 88–161 μg m–3 at the suburban Lalitpur site, and 40–74 μg m–3 at rural Dhulikhel on the eastern rim of the Kathmandu Valley. Meanwhile, PM10 ranged 194–309, 174–377, and 64–131 μg m–3, respectively. At the Ratnapark site, crustal materials from resuspended soil contributed an average of 11% of PM2.5 and 34% of PM10. PM2.5 was largely comprised of organic carbon (OC, 28–30% by mass) and elemental carbon (EC, 10–14% by mass). As determined by chemical mass balance source apportionment modeling, major PM2.5 OC sources were garbage burning (15–21%), biomass burning (10–17%), and fossil fuel (14–26%). Secondary organic aerosol (SOA) contributions from aromatic volatile organic compounds (13–23% OC) were larger than those from isoprene (0.3–0.5%), monoterpenes (0.9–1.4%), and sesquiterpenes (3.6–4.4%). Nitro-monoaromatic compoundsof interest due to their light-absorbing properties and toxicityindicate the presence of biomass burning-derived SOA. Knowledge of primary and secondary PM sources can facilitate air quality management in this region.

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Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 55%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Wintertime Air Quality across the Kathmandu Valley, Nepal: Concentration, Composition, and Sources of Fine and Coarse Particulate Matter

Islam

Mahata³

et al. 2022

ACS Earth Space Chem.

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“… 28 Other NAMaSTE papers involved with the source testing aspect of the campaign include Stockwell et al, who reported gas-phase emission factors and aerosol optical properties, and Jayarathne et al, 27 who reported off-line filter-based emission factors of fine aerosol (PM 2.5 ), organic carbon, elemental carbon, inorganic ions, organic molecular markers, trace metals, and PAHs. This work links the NAMaSTE source testing with ambient source apportionment work by Werden et al 30 that took place in the Kathmandu Valley in Nepal in 2015 and more recently. The AMS mass spectral profiles reported in this work are the first available for major undersampled sources in South Asia and important as such, but additional measurements could improve the representativeness or specificity available in the future.…”

Section: Introductionmentioning

confidence: 99%

Aerosol Mass Spectral Profiles from NAMaSTE Field-Sampled South Asian Combustion Sources

Goetz

Giordano

Stockwell

et al. 2022

ACS Earth Space Chem.

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Unit mass resolution mass spectral profiles of nonrefractory submicron aerosol were retrieved from undersampled atmospheric emission sources common to South Asia using a “mini” aerosol mass spectrometer. Emission sources including wood- and dung-fueled cookstoves, agricultural residue burning, garbage burning, engine exhaust, and coal-fired brick kilns were sampled during the 2015 Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) campaign. High-resolution peak fitting estimates of the mass spectra were used to characterize ions found within each source profile and help identify mass spectral signatures unique to aerosol emissions from the investigated source types. The first aerosol mass spectral profiles of dung burning, charcoal burning, garbage burning, and brick kilns are provided in this work. The online aerosol mass spectra show that organics were generally the dominant component of the nonrefractory aerosol. However, inorganic aerosol components including ammonium and chloride were significant in dung- and charcoal-fired cookstove emissions and sulfate compounds were major components of the coal-fired brick kiln emissions. Organic mass spectra from both the charcoal burning and zigzag brick kiln were dominated by nitrogen-containing ions thought to be from the electron ionization of amines and amides contained in the emissions. The mixed garbage burning emissions profiles were dominated by plastic combustion with very low fractions of organic markers associated with biomass burning. The plastic burning emissions were associated with enhanced organic signal at mass-to-charge (m/z) 104 and m/z 166, which could be useful fragment ion indicators for garbage burning in ambient aerosol profiles. Finally, a framework for the identification of emission sources using the unit mass resolution organic mass fractions at m/z 55 (f 55), m/z 57 (f 57), and m/z 60 (f 60) is proposed in this work. Plotting the ratio of f 55 to f 57 versus f 60 is found to be effective for the identification of emissions by the fuel type and even useful in separating emissions of similar source types. Although the sample size was limited, these results give further context to the aerosol and gas-phase emission factors presented in other NAMaSTE works and provide a critical reference for future aerosol composition measurements in South Asia.

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Brick kiln pollution and its impact on health: A systematic review and meta-analysis

Nicolaou,

Sylvies,

Veloso

et al. 2024

Environmental Research

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Pre-monsoon submicron aerosol composition and source contribution in the Kathmandu Valley, Nepal

Abstract: The Kathmandu Valley in Nepal suffers from unhealthy air quality, with mean pre-monsoon submicron particulate matter concentration (PM1) of 40 µg m-3 and daily peaks over 75 µg m-3. A...

Cited by 6 publications

References 139 publications

Wintertime Air Quality across the Kathmandu Valley, Nepal: Concentration, Composition, and Sources of Fine and Coarse Particulate Matter

Wintertime Air Quality across the Kathmandu Valley, Nepal: Concentration, Composition, and Sources of Fine and Coarse Particulate Matter

Aerosol Mass Spectral Profiles from NAMaSTE Field-Sampled South Asian Combustion Sources

Brick kiln pollution and its impact on health: A systematic review and meta-analysis

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